class_docstr: Stackdriver Hook for connecting with Google Cloud Stackdriver.
code: def _get_policy_client(self):
      if not self._policy_client:
          self._policy_client = monitoring_v3.AlertPolicyServiceClient()
      return self._policy_client
  
imports: from __future__ import annotations
  import contextlib
  import json
  from typing import TYPE_CHECKING, Any, Sequence
  from google.api_core.exceptions import InvalidArgument
  from google.api_core.gapic_v1.method import DEFAULT, _MethodDefault
  from google.cloud import monitoring_v3
  from google.cloud.monitoring_v3 import AlertPolicy, NotificationChannel
  from google.protobuf.field_mask_pb2 import FieldMask
  from googleapiclient.errors import HttpError
  from airflow.exceptions import AirflowException
  from airflow.providers.google.common.hooks.base_google import PROVIDE_PROJECT_ID, GoogleBaseHook
label_desc: Use image node_id 2 for calling the StackdriverHook obj's underlying member method code with example usage: obj._get_policy_client() and returns: self